A goal in the manufacture of diapers is to find a structure which is sufficiently inexpensive to manufacture and sell that it can be disposed of after a single use, yet has waste containment equivalent to cloth diapers, or cloth diapers with plastic overpants. One major problem in developing such a structure is to provide an appropriate, non-leaking fit around the leg openings. This search for an improved disposable diaper structure has been going on for the past two decades.
One method to achieve good leg fit in a rectangular disposable diaper is to use the so-called Z-fold configuration as described in U.S. Pat. No. RE 26,151.
Another method to achieve even better fit is to use elastic bands running length-wise along the sides of the diaper to provide elasticized leg openings, in-use and/or to shape the diaper into a non-rectangular (generally, "hourglass") shape that, in-use, conforms rather well to the legs. See U.S. Pat. No. 3,860,003.
In approaching this problem of leg openings, it may be speculated that it would be possible to improve leg fitment even further if the elastic bands could simply be provided in a curvlinear configuration. In-use, the curvilinear elastic would be fitted around the legs, substantially in the manner of circularly-elasticized non-disposable undergarments. Of course, this would require that the elastics be affixed to the diaper in a curvilinear configuration, rather than in the "in-line" elasticization mode used in all current elasticized disposable diapers. See U.S. Pat. No. 4,081,301 for a description of a preferred method for in-line elasticizaton of disposable diapers.
However, on further consideration it is clear that applying elastics in other than a substantially in-line configuration would be quite expensive and not conducive to the efficient, high-speed manufacture of disposable diapers.
The present invention provides a preferred structure for a disposable diaper, or the like, whereby elastics applied substantially in-line with the absorbent core are made to assume a curvilinear shape. This is achieved by constructing the diaper and folding it, in the manner described hereinafter. The resulting structure exhibits improved leg fitment, better waste containment, and is more comfortable than either folded (but non-elasticized) or in-line elasticized (but non-folded) diapers of the prior art.